SUBSTANCES PRODUCED BY BACTERIA 



169 



alcohol, to which is added alcoholic HCl (o.i mol. per liter). On cool- 

 ing, a precipitate is formed. This is recrystallized from absolute metha- 

 nol plus small amounts of HClj clusters of microscopic needles are ob- 

 tained, melting at 237-239° C, with decomposition j the specific rota- 

 tion is [a]'s = _ 102° ( I per cent in 95 per cent alcohol). Tyrocidine 



BACILLUS BREVIS BG 

 PEPTONE CULTURES 



ACID pH 4.8 



PRECIPITATE 



ALCOHOL EXTRACT 



precipitate 

 (tyrothricin) 



ACETONE -ETHER 



SOLUBLE PART 



CRYSTALLIZATION 



FROM ACETONE 



(GRAMICIDIN) 



INSOLUBLE PART 



CRYSTALLIZATION 



FROM ALCOHOL + HCL 



(TYROCIDINE HYDROCHLORIDE) 



Figure 17. Preparation of tyrothricin, gramicidin, and tyrocidine. From 

 Dubos (192). 



